Electromechanical actuator having ceramic insulation and method for production thereof

Abstract

The present disclosure relates to an electromechanical actuator, having a stack arrangement made of ceramic basis material having electromechanical properties and electrodes as well as a ceramic insulation for operation/use of the actuator in a humid environment. To ensure a long service life of the actuator with increased electromechanical expansion, an exemplary structure of the ceramic insulation has a smaller average grain size than the structure of the ceramic basis material. A method for the production of an actuator having ceramic insulation and a method for controlling such an actuator are also disclosed.

The invention claimed is: 
     
         1 . Electromechanical actuator comprising:
 a stack arrangement made of ceramic basis material having electromechanical properties;   electrodes; and   a ceramic insulation configured for operation of said actuator in a humid environment, wherein a structure of said ceramic insulation has a smaller average grain size than a structure of said ceramic basis material;   where said ceramic basis material and said electrodes are arranged along a stack axis and said stack arrangement comprises:
 two end faces aligned perpendicular to said stack axis and at least one side surface extending between said end faces, where said ceramic insulation on said at least one side surface extends from one end face to the other end face. 
   
     
     
         2 . Actuator according to  claim 1 , wherein a ratio of average grain size of the ceramic insulation structure to that of the ceramic basis material is selected to be one or more of ¾ or less, ½ or less, and/or ⅓ or less. 
     
     
         3 . Actuator according to  claim 1 , wherein an average grain size of said ceramic insulation structure is selected to be one or more of 20 μm or less, 5 μm or less, and/or 1 μm or less. 
     
     
         4 . Actuator according to  claim 1 , wherein an average grain size of the ceramic basis material decreases continuously towards said ceramic insulation, and/or beyond said ceramic insulation. 
     
     
         5 . Actuator according to  claim 1 , wherein said ceramic insulation is made of at least one or more of electromechanical, piezoelectric, and/or piezoceramic, material. 
     
     
         6 . Actuator according to  claim 1 , wherein said ceramic insulation is impermeable to water vapor/moisture. 
     
     
         7 . Actuator according to  claim 1 , wherein said ceramic insulation is made of at least one or more layers, where a total thickness of said ceramic insulation is at least one or more of 500 μm or less, 100 μm or less, and/or 60 μm or less. 
     
     
         8 . Actuator according to  claim 1 , wherein said ceramic insulation has substantially a same or a different material composition as/than said ceramic basis material. 
     
     
         9 . Actuator according to  claim 1 , comprising:
 two exterior electrodes for contacting said electrodes in said stack arrangement, arranged on a same outer surface or on two different outer surfaces of said actuator, where at least one electrode-free outer surface of said actuator includes said ceramic insulation.   
     
     
         10 . Actuator according to  claim 2 , wherein an average grain size of said ceramic insulation structure is selected to be one or more of 20 μm or less, 5 μm or less, and/or 1 μm or less. 
     
     
         11 . Actuator according to  claim 10 , wherein an average grain size of the ceramic basis material decreases continuously towards said ceramic insulation, and/or beyond said ceramic insulation.